ATtiny20 Atmel Corporation, ATtiny20 Datasheet - Page 138

• Manufacturer Part Number: ATtiny20
• Manufacturer: Atmel Corporation

Specifications of ATtiny20

• Flash (kbytes): 2 Kbytes
• Pin Count: 14
• Max. Operating Frequency: 12 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 5
• Hardware Qtouch Acquisition: Yes
• Max I/o Pins: 12
• Ext Interrupts: 12
• Usb Speed: No
• Usb Interface: No
• Spi: 1
• Twi (i2c): 1
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 8
• Adc Resolution (bits): 10
• Adc Speed (ksps): 15
• Analog Comparators: 1
• Resistive Touch Screen: No
• Temp. Sensor: Yes
• Crypto Engine: No
• Sram (kbytes): 0.12
• Self Program Memory: NO
• Dram Memory: No
• Nand Interface: No
• Picopower: No
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 1.8 to 5.5
• Operating Voltage (vcc): 1.8 to 5.5
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 2
• Output Compare Channels: 4
• Input Capture Channels: 1
• Pwm Channels: 3
• 32khz Rtc: No
• Calibrated Rc Oscillator: Yes

17. TWI – Two Wire Slave Interface
17.1
17.2
17.3
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Features
Overview
General TWI Bus Concepts
ATtiny20
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The Two Wire Interface (TWI) is a bi-directional, bus communication interface, which uses only
two wires. The TWI is I
bility with SMBus” on page
A device connected to the bus must act as a master or slave.The master initiates a data transac-
tion by addressing a slave on the bus, and telling whether it wants to transmit or receive data.
One bus can have several masters, and an arbitration process handles priority if two or more
masters try to transmit at the same time.
The TWI module in ATtiny20 implements slave functionality, only. Lost arbitration, errors, colli-
sions and clock holds on the bus are detected in hardware and indicated in separate status
flags.
Both 7-bit and general address call recognition is implemented in hardware. 10-bit addressing is
also supported. A dedicated address mask register can act as a second address match register
or as a mask register for the slave address to match on a range of addresses. The slave logic
continues to operate in all sleep modes, including Power down. This enables the slave to wake
up from sleep on TWI address match. It is possible to disable the address matching and let this
be handled in software instead. This allows the slave to detect and respond to several
addresses. Smart Mode can be enabled to auto trigger operations and reduce software
complexity.
The TWI module includes bus state logic that collects information to detect START and STOP
conditions, bus collision and bus errors. The bus state logic continues to operate in all sleep
modes including Power down.
The Two-Wire Interface (TWI) provides a simple two-wire bi-directional bus consisting of a serial
clock line (SCL) and a serial data line (SDA). The two lines are open collector lines (wired-AND),
and pull-up resistors (Rp) are the only external components needed to drive the bus. The pull-up
resistors will provide a high level on the lines when none of the connected devices are driving
the bus. A constant current source can be used as an alternative to the pull-up resistors.
Phillips I
SMBus compatible (with reservations)
100 kHz and 400 kHz support at low system clock frequencies
Slew-Rate Limited Output Drivers
Input Filter provides noise suppression
7-bit, and General Call Address Recognition in Hardware
Address mask register for address masking or dual address match
10-bit addressing supported
Optional Software Address Recognition Provides Unlimited Number of Slave Addresses
Slave can operate in all sleep modes, including Power Down
Slave Arbitration allows support for SMBus Address Resolve Protocol (ARP)
2
C compatible
2
C compatible and, with reservations, SMBus compatible (see
144).
8235B–AVR–04/11
“Compati-